I believe it is a better idea to use a specialised lubricant for locks, as wd-40 or other regular lubricants will accumulate dust/particles and worsen the situation.I would first try spraying some WD-40 in it and see if it works. Pins could be just gummed up. If it has to be taken apart, you will either need a locksmith or a new lock. Depending on what it is, a new lock might be cheaper. You didn't say what lock it is, the ignition or something else.
my 86a had the same problem,once i dug all the little pieces out she went back to workingon my 85 1200 ltd my trunk locks would get blocked, there where peices of white plastic inside the lock that where comming loose due to age. i took a small pick and dug them out and they still work.